Pulverized-fuel burner



April 11, 1939. R. .1. c. BQUDRANT 2,154,320

FULVERIZED-FUEL BURNER Filed Marfch 10, 1937 4 Sheets-Sheet l z df hApril 1 1, 1939 R. J. c. BoUDRA-r 2,154,320

PULVERI ZED-FUEL BURNER Filed Maron 10, 1937 4 sheets-sheet 2 April 11,1939. R. J. c. BOUDRANT v PULVERIZED-FUEL BURNER Filed 'March 10, 1957 4Sheets-Sheet 3 wwf gw April 11, 1939 R. J. c. BOUDRANT 2,154,320

FULVERI ZED -FUEL BURNER Filed March lO, 1937 4 Sheets-Sheet 4 Fig. 4

f Patented Apr. 1l, 1939 Robert Jean Charles Boudrant, Paris, France,assignor to Socit dElectricit de Paris, Paris, France, ajoint-stockcompany of France Application March -1o, 1937, serial InFrance March 25, 1936 'I'his invention relates to pulverized-fuelburners and has for its object to ensure the com-i bustion of thepulverized fuel as completely and rapidly as possible.

539.: It is known that in burners of large dimensions, very greatdifficulties are encountered in obtaining a homogeneous mixture of airand coal. There occurs either an excessive elongation of the flame `orconsiderable loss by solid. unburnt loffparticles resulting fromincomplete combustion.

The invention provides for obtaining, with `a burner of large rating, afuel-comburent jet as.r

homogeneous as possible; it consists in dividing the flow of primary airandfuel into several equal )s-streams or sections and interposingbetween them alternate streams of secondary air in suitable proportion.f

In order to secure at the mouth of the burner' the desired mixturebetween the streams of 20' secondary air and those LVof primary air andfuel, i

the latter are injected, not in a continuous manner, but intermittentlyin order to produce pulsations of high frequency. y Upon theaccompanying drawings to which 25 reference is made in the subsequentdescription, there has rbeen represented by way of example, one form ofconstruction of the improved compound burner.

Fig. 1 shows in its upper half a sectional eleva- 30 tion along the axisof the apparatus and in its lower half an elevation, only the casing forsecondary air being in section.

Fig. 2 is a front view of the apparatus, from which the rotary mixer hasbeen removed. g Figs. 3 and 4 are half sections taken respectively alongthe lines 3-3 and 4 4 of Fig. l. In all these figures the same referencenumerals designate the same parts or elements.

Within the pipe supplying pulverized coal and 4 primary air is mounted arotary mixer I, Fig. 1, preferably of the kind described in my pendingapplication Serial No. 102,215, filed Sept. 23, 1936, which ensuresthorough mingling of the primary air and fuel mixture before itsentrance to a 4,-, divider 2.

The divider 2, Figs. l, 2 and 3, is composed of iron or steel wallsresting against one another in pairs, forming a star with any suitablenumber of branches; these walls constitute the `anks of 5u ducts 3,Figs. 3 and 4, for the passage of the primary air and fuel current, thewalls resting at their central parts upon a hollow cone 4, Figs. 1 Y and3, and being closed at the periphery so as to form fluid-tight conduitsopen only at their two 55 ends.

s claims. 'n (o1. 11o-V104)V The ducts 3 eachI maintain an approximatelyconstant cross-sectional area as far as the mouth of the burner, butthey increase in radial height While decreasing in angular widthregularly from the entrance to the exit. The free spaces or channels 5,Figs. 1, 3 and 4, thus provided between adjacent ducts 3, have across-sectional area which is nil at the entrance to the divider andmaximum at the burner outlet.

These channels 5 are all in communication at their periphery with theLchamber 6, Figs. 1 and 3, constituting the secondary air casing, and attheir ends they open 'out into the combustion space.

Within the opening into the combustion space, two angularly adjustableshutters 1, Figs. 1 and 4, are placed in each channel 5; they allowregulation both of the supply of secondary air and of the angularrelation of the streams of secondary air towards the streams of primaryair and fuel.

All the shutters 1 can be operated simultaneously by a device such asrepresented at 8, Figs. 1 and 2, or any other analogous device.

The hollow central cone 4 is provided with an adjustable register 9,Figs. 1 and 4, controlled by a hand wheel Il), Figs. 1 and 2, from theexterior of the burner.

This register allows of uncovering more or less a plurality of slots Il,Figs. 1 and 4, for communication between the secondary air casing 6 andthe interior of the central cone 4 so as to be able to admit more orless air to the very centre of the flame and thereby to lengthen orshorten the flame according to the nature of the coal being burnt or theneeds of combustion.

It will be readily understood that upon the passage of one of the bladesof the second or downstream screw rotor of the rotary mixer l in frontof one of the ports or apertures of the divider 2, a supplementary lossof head will be set up at the entrance to this aperture; since thisoperation takes place three or four times for each revolution of themixer l according as the rotor in question is fitted with three or withfour blades, there is produced a high frequency pulsatory action for theinjection of the primary air and fuel current.

This pulsation is extremely favorable to the mixing of the primary andsecondary currents at the exit from the-burner and it improves thecombustion to a considerable extent.

In large burners, it is advantageous to increase the pulsating effect bycausing the rotor blades or the rotor spindle to carry a set of ilatshutters (not shown in the drawings) having the shape of one of thedivider ports, the plane containing these shutters being perpendicularto the common axis of the rotary mixer.

The burner described above is of the radiant type, possessing an axis ofsymmetry, but it is naturally permissible without departing from thescope of the invention, to arrange the component parts of this burner ina different way so as to produce modifications operating practically inthe Same Way.

The number of ducts is a function of the dimensions of the burner; byway of illustration, it is eight in the drawings. It is advantageous toincrease that number in the case of a very large burner.

What I claim is: n l

1. In a pulverizedff'uel burner, a pipe supplying a current of primaryvair containing pulverized fuel, two rotary mixing devices in said pipe,eachv of said mixing devices comprising a helically bladed rotor adaptedfor revolving by said cur' rent, one of said rotors having right handedblades and the other left handed blades, and the two rotors beingarranged coaxially, one immediately behind the other, said mixingdevices adapted to homogenize the mixture of air and fuel in saidcurrent, means for dividing said homogenized current into a plurality ofstreams, said dividing means including a plurality of substantiallyequal ports, said mixing devices having blades rotating in proximity tothe ports of said dividing means, a plurality of ducts conveying saidstreams, said ducts being spaced around the axis of said pipe andincreasing in radial height while decreasing in angular width towardsthe burner mouth, a casing for supply of secondary Y air, said casingbeing in communication with the spaces between said ducts. and means forregulating the mixture 0f secondary air from said spaces with saidprimary air streams at the :burner mouth.

2. In a pulverized fuel burner, a pipe for supplying a current ofprimary air containing pulverized fuel, means for rendering said currentsubstantially homogeneous, means for dividing said homogenized currentinto a plurality of streams, a plurality of ducts conveying saidstreams, said ducts being spaced around the axis of said pipe andincreasing in radial height while decreasing in angular width towardsthe burner mouth, a hollow open-ended cone aligned with said axis andforming a divergent core to said ducts, the base of said cone being openin the direction of discharge from said ducts, a casing for supply ofsecondary air, said casing being in V'communication with the spacesbetween' said ducts, said cone having a plurality of apertures incommunication with the spaces between said ducts, means for regulatingthe flow of secondary air from said spaces through said slots into saidcone, and means for regulating the mixture of secondary air from thedischarge ends of said spaces with said primary air streams at theburner mouth.

3. A pulverized fuel burner, comprising a pipe supplying a current ofprimary air containing pulverizedfuel, means for homogenizing themixture of air and fuel in said current, means for dividing said currentinto a plurality of substantially homogeneous streams spaced about anaxis in line with the axis of said pipe, means located adjacent to saiddividing means for setting up pulsating effects in said streams, meansfor interposing streams of secondary air between said spaced streams,and controllable means for mixing said streams, said controllable meansproviding for regulation of the speed and direction of said secondaryair independently of its amount.

ROBERT JEAN CHARLES BOUDRANT.

